It is well known for lubricating oils to contain a number of additives used to protect the engine from wear, soot deposits and acidity build up. Common additives for engine lubricating oils include zinc dialkyldithiophosphate (ZDDP) an antiwear additive, and overbased calcium sulphonate and calcium phenate detergents. It is believed that ZDDP antiwear additives protect the engine by forming a protective film on metal surfaces. Detergents such as overbased calcium sulphonate help keep the engine parts clean of soot and other deposits, and offer an alkalinity reserve. Typical treatment quantities of ZDDP range from 1 to 2 weight percent based on the total weight of the lubricant. Typical treatment quantities of overbased calcium sulphonate range from 0.05 to 5 weight percent based on the total weight of the lubricant.
In recent years phosphorus compounds and sulphur (from sulphonates, sulphur-containing phenates, and other materials such as metal-containing dithiophosphates) derived from engine lubricants have been shown to contribute in part to particulate emissions. Also, sulphur and phosphorus tend to poison the catalysts used in catalytic converters, resulting in a reduction in performance of said catalysts.
However, any reduction in the amount of ZDDP or overbased calcium sulphonates or phenates will reduce the antiwear, detergent, and reserve alkalinity properties of the lubricant. Therefore there is a need for an additive package that will reduce sulphur and phosphorus content without having an adverse effect on these properties of lubricant oil.
U.S. Pat. No. 6,310,009, Kocsis et al., Oct. 30, 2001, relates to the use of saligenin derivatives used in lubricating compositions. The formulations contain borated or non-borated magnesium saligenin derivatives. These compositions exhibit improved seal compatibility and reduced copper and lead corrosion.
U.S. Pat. No. 6,200,936, Moreton, Mar. 13, 2001, relates to the use of salixarate compounds as an additive for finished lubricating oils. The compositions disclosed are particularly suitable for medium or low speed diesel engines, especially four-stroke trunk piston engines.
PCT publication WO 01/56968, Aug. 9, 2001, relates to the use of salixarate type compounds used in lubricating oils. The compositions disclosed are particularly suitable as thermal stabilisers for medium or low speed diesel engines.
The present invention provides an additive formulation for lubricating oils capable of decreasing sulphur and phosphorus containing emissions. It further can lead to decreased engine wear and decreased corrosion. The invention further provides an additive formulation for lubricating oils with low phosphorus and sulphur content capable of meeting or exceeding current requirements of engine cleanliness, wear protection, and alkalinity. It further provides an additive formulation for lubricating oils capable of producing reduced amounts of ash and capable of improving seal compatibility.